WASHINGTON — A potential return to operations of satellite megaconstellation company OneWeb is a new source of worry for astronomers who previously had been focused on the effect SpaceX’s Starlink satellites will have on their observations.
OneWeb, which filed for Chapter 11 bankruptcy in March, announced July 3 that the British government and Indian telecom company Bharti Global will provide $1 billion in new funding to recapitalize the company. That offer is pending approval by a U.S. bankruptcy court at a July 10 hearing.
OneWeb said that the new funding would allow the company to “effectuate the full end-to-end deployment of the OneWeb system,” but didn’t elaborate on those plans. The company suspended launches after the Chapter 11 filing after placing 74 satellites of an initial 650-satellite constellation into orbit. However, in May the company filed a proposal with the U.S. Federal Communications Commission seeking to increase its constellation by 48,000 satellites.
The prospect of a recapitalized OneWeb resuming launches of hundreds, or potentially tens of thousands, of satellites is a new concern for astronomers. Those satellites, astronomers said during sessions July 3 of the European Astronomical Society’s annual conference, held online, are a particular concern because of their higher altitudes.
“The big problem is low Earth orbiting satellites much higher than 600 kilometers,” said Tony Tyson, chief scientist for the Vera Rubin Observatory, a wide-field telescope under construction in Chile. The higher a satellite’s altitude, the longer it is visible after sunset and before sunrise. “They’re illuminated all night long in the summertime.”
OneWeb’s satellites operate at an altitude of 1,200 kilometers. While too dim to be seen with the naked eye — they are at approximately eighth magnitude — they are still bright enough to pose a problem for professional astronomers.
“It is clear that a huge constellation of 50,000 satellites at high altitude is the most threatening to visible astronomy,” said Olivier Hainaut, an astronomer at the European Southern Observatory who has modeled the effect of satellite constellations on groundbased astronomy.
At the time of OneWeb’s Chapter 11 filing, the company had only just started to discuss with astronomers the impact of their satellites on observations. A working group of the American Astronomical Society had one teleconference with OneWeb about the topic before the bankruptcy.
Some astronomers said at the conference they will look to the British government, as one of the new owners of OneWeb, to intervene on the subject. “We have not heard anything from the U.K. government,” Hainaut said during a conference session just a few hours after OneWeb announced the deal.
Robert Massey, deputy executive director of the Royal Astronomical Society, said in a press briefing after the conference sessions that OneWeb did participate in a meeting his society held in January on the issue. “We thought they’d disappeared” after their bankruptcy filing. “Then, weirdly, they filed this license application for 48,000 satellites, which took people by surprise.”
“I would hope that the U.K. government uses its leverage that it now has to help ensure that they are good a partner in this and they engage with the astronomy and space science community,” he said.
Waiting on VisorSat
Astronomers at the meeting contrasted OneWeb with SpaceX, whose initial launches of Starlink satellites more than a year first raised the alarm among astronomers about the effect such satellites would have on their observations.
Since the initial Starlink launch in May 2019, astronomers have met regularly with SpaceX, and the company has made efforts to reduce the brightness of its satellites. In January, it launched an experimental satellite dubbed “DarkSat” with darkened surfaces intended to make the satellite less reflective. In June, it started launching “VisorSats,” Starlink satellites equipped with sunshades to block sunlight from hitting reflective surfaces.
The first VisorSat has yet to reach its operational orbit, and thus astronomers can’t yet determine how effective it is. “There are many people who are going to measure it as soon as it is in position,” said Hainaut at the press briefing. “It is a matter of weeks.”
Astronomers hope that VisorSat will be significantly dimmer than unmodified Starlink satellites, with a goal of reaching seventh magnitude. “We are pretty sure that seventh magnitude for the satellite would get us out of woods” in terms of the worst effects the satellites would have on Rubin Observatory observations, Tyson said.
Starlink satellites will still leave a trail on images that will interfere with observations, but Tyson praised SpaceX for making efforts to mitigate the worst effects of the constellation. “It seems like the SpaceX brightness mitigation efforts are on track and actually set an example for the industry to follow,” he said.
Patricia Cooper, SpaceX vice president of satellite government relations, said at the conference that the company has taken other measures to mitigate the effect of Starlink on astronomy, including lowering the altitude of some of its satellites from 1,100 to 550 kilometers, a move that also benefits safety of space operations. “I don’t expect us to fly any of our future satellites at higher altitudes,” she said.
Cooper credited “robust and frank talk” between the company and astronomers, many of whom were sharply critical of Starlink when launches started last year, for driving those improvements. “We’ve done our contribution in raising awareness that constellations can be a problem for astronomy,” she said. “We’re a venture that attracts a lot of attention, for better or worse.”